The Data Coordinating Center (DCC) of the NHLBI PTCA Registry proposes to be the DCC of the Bypass Angioplasty Revascularization Investigation (BARI) to test the relative efficacy of Coronary Artery Bypass Graft Surgery (CABG) and Percutaneous Transluminal Coronary Angioplasty (PTCA) in patients with multivessel coronary artery disease and severe angina. The DCC will participate with NHLBI and the clinical investigators in the design and execution of the multicenter, randomized clinical trail and a comprehensive registry of patients with angiographically confirmed symptomatic coronary artery disease (CAD). The Principal Investigator, Katherine Detre, M.D., Dr. P.H., has directed the Data Coordinating Center for the NHLBI PTCA Registry since 1980, and has coordinated the VA Bypass Study since 1973. From our participation in these two studies, we have both the data and the experience to provide the framework for planning BARI. The PTCA Registry data will be invaluable to provide estimates for proposed endpoint measures and for sample size projections. With clinical investigators participating in the Registry, we have already considered and solved many of the same problems regarding data collection, follow-up schedules definitions of outcome and baseline disease characteristics, statistical analysis, and interpretation of findings that are likely to arise with BARI. For BARI, we propose a distributed data entry system consisting of IBM microcomputers which will be used to record on-site data at baseline and follow-up of 1,800 trial patients and perhaps as many as 30,000 BARI registry patients. Data will be transferred to Pittsburgh and maintained and analyzed on a VAX 8200 computer. Our group will take responsibility for randomization and interim monitoring for the trial. For both registry and trial, we will prepare data collection forms, draft the manual of operations, implement quality control measures and carry out statistical analyses. Our Data Center has made evaluation of PTCA its most important project since 1980 and is now prepared to undertake BARI.